作业12

#include<stdio.h>
#include <iostream>
#include<string.h>
using namespace std;
 
char *reserved[6] = {"begin","if","then","while","do","end"};
char input[80],output[8];
char ch;
int syn,p,i;//syn为种别码,p为扫描与添加
int m = 0,n,row,sum = 0,count=0;
int flag = 0;//标志位
void ParseS();//解析语句
void ParseS1();
void ParseS2();
void ParseS3();
void ParseS4();
void ParseC();//解析条件
void ParseE();//解析表达式
void ParseE1();
void ParseT();//解析项
void ParseT1();
void ParseF();//解析因子
void scanner(){
    for( i = 0 ; i < 8 ; i++ ){
        output[i] = NULL;
    }//初始化输出
    ch = input[p++];
     
    while( ch == ' ' ){
        ch = input[p] ;
        p ++ ;
    }
    //持续读入
    if( ( ch >= 'a' && ch <= 'z' ) || ( ch >= 'A' && ch <= 'Z' ) ){
        m = 0 ;
        while( ( ch >= 'a' && ch <= 'z' ) || ( ch >= 'A' && ch <= 'Z' ) || ( ch >= '0' && ch <= '9' ) ){
            output[m++]  = ch ;
            ch = input[p++];
        }
        output[m++] = '\0';
        p -- ;
        syn = 10 ;
        for( n = 0 ; n < 6 ; n ++ ){
            if( strcmp(output,reserved[n]) == 0 ){
                syn = n + 1;
                break;
            }
        }
     
    }else if( ( ch >= '0' && ch <= '9' ) ){
        sum = 0 ;
        while( ch >= '0' && ch <= '9' ){
            sum=sum*10+ch-'0' ;
            ch = input[p++] ;
        }
        p -- ;
        syn = 11;
    }
    else if(ch == '/'){
        ch = input[p++] ;
        if(ch == '/'){
            while(ch != '\n'){
                ch = input[p++] ;
            }
            scanner();   
             
        }
        else if(ch == '*'){
            ch = input[p++];
            int flag=0;
        //    printf("%c %c",ch,input[p]);
            while((ch == '*' && input[p] != '/')||(ch != '*' && input[p] == '/') || (ch != '*' && input[p] != '/')){
                ch = input[p++] ;
                if(p==count-2 && (ch != '*' && input[p] != '/')){
                    flag =1;
                    syn = 100;
                    break;
                }
            }
            p++;
            if(flag==0){
                scanner();   
            }
             
        }else{
            p = p - 2 ;
            ch = input[p++] ;
            output[0] = ch ;
            syn = 16 ;
        }
         
    }else switch(ch){
        case '+':
            output[0] = ch ;
            syn = 13;
            break;
        case '-':
            output[0] = ch ;
            syn = 14;
            break;
        case '*':
            output[0] = ch ;
            syn = 15 ;
            break;
        case '/':
            output[0] = ch ;
            syn = 16 ;
            break;
        case ':':
            i = 0;
            output[i++] = ch ;
            ch = input[p++];
            if( ch == '=' ){
                output[i++] = ch;
                syn = 18 ;
            }else{
                syn = 17;
                p-- ;
            }
            break;
        case '<':
            i = 0 ;
            output[i++] = ch ;
            ch = input[p++] ;
            if( ch == '=' ){
                output[i++] = ch ;
                syn = 21 ;
            }else if( ch == '>' ){
                output[i++] = ch ;
                syn = 22 ;
            }else{
                syn = 20 ;
                p-- ;
            }
            break;
        case '>':
            i = 0;
            output[i++] = ch ;
            ch = input[p++] ;
            if( ch == '=' ){
                output[i++] = ch;
                syn=24;
            }else{
                syn=23;
                p--;
            }
            break;
        case '=':
            output[0] = ch ;
            syn = 25 ;
        break;
        case ';':
            output[0] = ch ;
            syn = 26 ;
            break;
        case '(':
            output[0] = ch ;
            syn = 27 ;
            break;
        case ')':
            output[0] = ch ;
            syn = 28 ;
            break;
        case '#':
            output[0] = ch ;
            syn = 0;
            break;
        case '\n':
            syn = 99 ;
            break;
        default:
            syn = -1 ;
            break;   
    }
     
}
 
void ParseS(){
    if(flag != 0){
        if(syn == 10){ //<id>:=<表达式>
            scanner();
            ParseS1();
        }
        else if(syn == 2){ //if
            scanner();
            ParseS2();
        }
        else if(syn == 4){//while
            scanner();
            ParseS3();
        }
        else if(syn == 0){
        }
        else{
            printf("statement syntx error S\n");
            exit(0);
        }
    }
    else{
        if(syn == 1){//begin
        scanner();
        flag = 1;
        ParseS4();
        }else{
            printf("error,缺少begin!\n");
            exit(0);
        }
    }
}
 
void ParseS1(){
    if(syn==18){
        scanner();
        ParseE();
    }
    else{
        printf("statement syntx error S1\n");
        exit(0);
    }
}
void ParseS2(){//if
    ParseC();
    if(syn== 3 ){
        scanner();
        ParseS();
    }
    else{
        printf("statement syntx error S2\n");
        exit(0);
    }
}
void ParseS3(){//while
    ParseC();
    if(syn== 5 ){
        scanner();
        ParseS();
    }
    else{
        printf("statement syntx error S3 \n");
        exit(0);
    }
}
 
void ParseS4(){//begin
    ParseS();
    while(syn == 26){
        scanner();
        ParseS();
    }
    if(syn == 6){
        scanner();
        if(syn == 0){
            printf("success!");
        }
        else{
            printf("statement syntx error S4\n");
        }
    }
    else{
        printf("error,缺少end\n");
        exit(0);
    }
}
void ParseC(){
    ParseE();
    if(syn==25||syn==0||syn==20||syn==21||syn==23||syn==24){
        scanner();
        scanner();
    }
    else{
        printf("condition syntx error C\n");
        exit(0);
        }
    ParseE();
  
}
void ParseE(){
    ParseT();
    ParseE1();
 
}
  
  
 
void ParseE1(){
    if(syn == 13 || syn == 14){
        scanner();
        ParseT();
        ParseE1();
    }
    else if(syn == 28 || syn == 0){
    }   
}
 
  
 
void ParseT(){
    ParseF();
    ParseT1();
}
 
  
 
void ParseT1(){
    if(syn == 15 || syn == 16){
        scanner();
        ParseF();
        ParseT1();
    }
    else if(syn == 13 ||syn == 14 || syn == 28 || syn == 0){   
    }
 
}
 
void ParseF(){
    if(syn == 27){
        scanner();
        ParseE();
        if(syn == 28){
            scanner();
        }
        else{
            printf("factor syntx error F\n");
            exit(0);
        }
    }
    else if(syn == 10 || syn == 11){
            scanner();   
                 
    }
    else{
        printf("factor syntx error F\n");
        exit(0);
    }
}
int main() {
    p = 0;
    printf("请输入源程序：");
    do{
        ch = getchar();
        input[p++] = ch;
    }while(ch != '#');
    count = p;
    p = 0;
    scanner();
    ParseS();
    return 0;
}
 
 
posted @ 2019-11-29 21:44 162 阅读(109) 评论(0) 收藏举报
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作业12

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